1. Field of the Invention
The present invention relates to a display device to indicate positive and negative display values by increasing or decreasing a number of display elements which are lit, and, more particularly, the present invention relates to a display device used in a camera or exposure meter having an expanded display range in a limited analog display area.
2. Description of the Related Art
Cameras which have a display section to indicate various states of the camera are known. To meet the diverse needs of the user, the display section may be provided inside of or outside of a viewfinder in a limited display area of the display section. The display section of the camera may include different types of digital display of numerical values, such as the shutter speed and aperture settings, as well as analog display of the exposure value (hereinafter referred to as "EV") during the manual exposure control mode.
The known display sections for displaying an EV include multiple symbol display elements (hereinafter referred to as "display segments") arranged in a single row in the display area of the display section. A specified number of the symbol display segments are interconnected and extend in a positive or a negative direction from the location of an origin, which is the central area of the row of the multiple symbol display segments. The display segments are lit according to a discrepancy between a photometric value and a set value (.+-..DELTA.EV), as well as a positive or negative value.
FIG. 16 shows an example of the configuration of a conventional EV display section. As shown in FIG. 16, the conventional EV display section consists of a fixed display section 35 and variable display sections 31-34 and 36-39. Each of the fixed display section 35 and the variable display sections 31-34 and 36-39 consist of liquid crystal display (LCD) display segments.
The fixed display section 35 consists of a positive ("+") display section 35a, an origin "0" display section 35f, and a negative ("-") display section 35j. Display segment 35e in the origin display section 35f is used to indicate that exposure is correct. Display segment 35b in the "+" display section 35a is at a position indicating an exposure value of +1 [EV] over correct exposure. Display segment 35i in the "-" display section 35j is at a position indicating an exposure value of -1 [EV] under correct exposure. Display segments 35c, 35d, 35g, and 35h are at positions indicating increments in exposure value of 1/3 [EV].
In the fixed display section 35, all of the display segments 35a-35j are driven in a consolidated manner to be lit or extinguished by a common signal. Therefore, all of the display segments 35a-35j are always lit while displaying the exposure value. However, each symbol display segment 31-34 and 36-39 in the variable display section is arranged in a single, horizontal row, and the display segments 31-34 and 36-39 are individually and independently driven to be lit or extinguished. A measured difference between the photometric value and the set value (.+-..DELTA.EV) is displayed by increasing or decreasing the number of display segments 31-34 and 36-39 that are lit.
In the conventional display section shown in FIG. 16, the fixed display section 35 is lit during the manual exposure control mode. While the fixed display section 35 is lit during manual exposure control mode, the step between the .+-.[EV] range and the state that exceeds the range is indicated by the variable display section 31-34 and 36-39, as will be described in detail below, thereby visually displaying .DELTA.EV.
More specifically, when .DELTA.EV is 1/3[EV] over correct exposure, the symbol display segment 34 is lit in addition to the fixed lighting of display segment 35e, which indicates the correct exposure. When .DELTA.EV is 2/3[EV] over correct exposure, symbol display segments 33 and 34 are lit in addition to the fixed lighting of display segment 35e. When .DELTA.EV is +1 [EV], symbol display segments 32-34 are lit in addition to display segment 35e. When .DELTA.EV exceeds correct exposure by +1[EV], all of display segments 31-34 located on the over exposure side with reference to the position of the origin "0" are lit in addition to the fixed lighting of display segment 35e.
Similarly, when .DELTA.EV is 1/3[EV] under correct exposure, symbol segment 36 is lit in addition to the fixed lighting of display segment 35e which indicates the correct exposure. When .DELTA.EV is 2/3[EV] under correct exposure, symbol display segments 36 and 37 are lit in addition to the fixed lighting of display segment 35e. When .DELTA.EV is 1[EV] under correct exposure, symbol display segments 36-38 are lit in addition to the fixed lighting of display segment 35e. When .DELTA.EV exceeds 1[EV] under correct exposure, all of symbol display segments 36-39 located on the under exposure side with reference to the position of the origin "0" are lit in addition to the fixed lighting of display segment 35e.
As described above, a change of .DELTA.EV from the origin "0" to the over (under) exposure side of up to +1 (-1) [EV] is indicated in analog form by increasing or decreasing the displayed exposure value incrementally with 1/3[EV] step changes. When the change of .DELTA.EV on the over (under) exposure side exceeds +1 (-1) [EV], all of symbol display segments 31-34 (36-39) located on the over (under) exposure side with reference to the position of the origin "0" are lit, thereby enabling a user to identify whether .DELTA.EV is within .+-.1[EV].
The type of display method illustrated in FIG. 16 may be applied not only to display a discrepancy during manual exposure, but also to display an instance wherein the deviation from a numerical value used as a reference value can be indicated through steps in an analog form. For example, the display of FIG. 16 can be used to indicate an exposure correction amount, a light adjustment correction amount, or the difference in exposure between central-oriented photometry and multiple photometry.
When the deviation from a numerical value used as the reference value is indicated through steps in analog form, unlike the indication of a numerical value, a designated area is required for positioning the multiple symbol display segments. Furthermore, the indication range is stipulated based on the number of segments that can be positioned in the designated area.
However, as noted above, it is difficult to maintain sufficient area for an analog display in a display section having various display indicators. Thus, the analog display area tends to be smaller and cannot meet the needs of users who require an expanded display range. More specifically, a conventional camera is only capable of indicating the discrepancy amount up to .+-.1 [EV] for users who actually want an indication of up to .+-.2 [EV]. Furthermore, some users want an indication of the discrepancy amount .+-..DELTA.EV of up to .+-.3 [EV].
In order to achieve the requirements of those users wanting an expanded display range, an analog display area in the display section may be expanded. However, expanding the analog display area will eliminate display area used to display information preferred by other users, for example, those who require display of numerical values.